Recursion On Initialization
Apr 29, 2014
I am trying to make a game, for some reason i have begun to get a java.lang.StackOverflowError.
I am not exactly sure how i can fix it. only removing line 14 from infopannel1 (and everything that used that class.) seems to work. im not sure what else i can do to fix it. or why its resulting in stack overflow for that matter.
I am putting in a link for the files i wrote this using bluej (several classes have no relevance, errorv2, demonstration, folderreadertest, ReadWithScanner, saveloadtest, menutest,rannum, and menutestTester. are all irrelivent to my problem.)
[URL] .....
View Replies
ADVERTISEMENT
Dec 20, 2014
I come from a C++ background and I recently started learning Java from "Thinking in Java" 4th Edition by Bruce Eckel.What's the difference between:
// explicit in class initialization
// saw this on page 126
class A {
}
public class B {
A obj1 = new A();
A obj2 = new A();
}
and
// non static instance initialization
// saw this on page 132
class A {
}
public class B {
A obj1;
A obj2;
{
obj1 = new A();
obj2 = new A();
}
}
View Replies
View Related
Sep 17, 2014
I came across this code which proves that variable initialisation occurs before even constructors are called.However, I am confused over some things.
Firstly, from my understanding, when a new House object is created in this line House h = new House(); , the no-arg constructor of the House class is called.
Since the no-arg constructor House() is called, why are all the creation of Window objects being run first ? Shouldn't Java jump straight into the no-arg constructor House() ?
class Window {
Window(int marker) { System.out.println("Window(" + marker + ")"); }
}
class House {
Window w1 = new Window(1); // Before constructor
House() {
// Show that we’re in the constructor:
System.out.println("House()");
w3 = new Window(33); // Reinitialize w3
[code]...
View Replies
View Related
May 12, 2014
I am using netbeans 7.2, glassfish 3.1.2, JSF 2.1 and Primefaces 3.2. When I add more than three menu tabs, I get this error ui layout initialization error the center-pane element does not exist the center-pane is a required element. This is my template.xhtml code:
<?xml version='1.0' encoding='UTF-8' ?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml"
xmlns:ui="http://java.sun.com/jsf/facelets"
xmlns:h="http://java.sun.com/jsf/html"
xmlns:p="http://primefaces.org/ui">
[Code] ....
View Replies
View Related
Sep 9, 2014
public class SavingsAccount extends Account {
private static final double MIN_BALANCE = 100.00;
private static final double RATE = 0.035;
public SavingsAccount(Customer customer, double bal, String accountNum,
Transaction[] trans) {
super(customer, bal, accountNum, trans);
[code]....
When I execute this code there is an error in Transaction array initialization. Change the Saving account constructor from (String customer,double balance, String accountnumber,Transaction[] tr) to (String customer,double balance, String accountnumber,Transaction tr)
View Replies
View Related
Apr 2, 2015
What static initialization blocks do in java?
View Replies
View Related
Mar 20, 2015
I have a question related to q44 of Examlab.
public static void main(String... args) {
String i;
// String i = null; that would compile
if (i == null) {// this line does not compile as i was not initialized
System.out.print("A");
} else {
System.out.print("B");
i = "A";
main("A", "B");
}
}
Why does the above code not compile although the statement String i should lead to an initialisation of i to the value of null which is the default value for Strings.
View Replies
View Related
Feb 20, 2014
I remember reading Instance variables & local variables (in methods) are initialized to appropriate value by the compiler.
Is this true for static class variables and variables in nested classes ?
View Replies
View Related
May 12, 2014
I am trying a simple program to access ServletConfig initialization parameter in a jsp. But I am not clear how its working. This is web.xml
<web-app>
<servlet>
<servlet-name>Myservlet</servlet-name>
<jsp-file>/JjspInit.jsp</jsp-file>
<init-param>
<param-name>para</param-name>
<param-value>valu</param-value>
[Code] ....
Now If I hit /Allen it sets init parameter for both servlet MyServlet and jsp JjspInit. I don`t have any servlet all I have is a web.xml and a jsp page. But accessing JjspInit.jsp directly gives null.
How hiting the url /Allen prints valu. This code is on JjspInit.jsp .
So does that mean that in web.xml I have registered this jsp as the target for /Allen. And one more question directly accessing the jsp page shows null it means init parameter haven`t been set.
View Replies
View Related
Aug 15, 2014
if, instead of an ArrayList, can I do the following to initialize a Dyanmic array ? :
First, in my class, I have :
class Example{
private int rows;
private int columns;
private AnotherClass[][] 2DArray;
public Example(int rows, int columns){
this.rows = rows;
this.columns = columns;
[code]....
View Replies
View Related
Jan 13, 2015
I want to initialize my servlet based on the scope of my application.
For example, I have multiple admins with their respective email address.
I want to perform action within my servlet based on the given environment.
Would this be the right approach, if I set the admin email addresses in my web.xml as init-param:
<servlet>
<servlet-name>ServletName</servlet-name>
<servlet-class>com.mkyong.ServletDemo</servlet-class>
<init-param>
<param-name>admin1</param-name>
[Code] .....
Now if I am in the admin 1 environment, I would initialize my servlet with request parameter admin=1 and the servlet should load email address of admin 1 and similarly when in the environment 2, should load the servlet with admin 2.
call environment 1:
/servlet/Demo?admin=1
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws IOException{
[Code] .....
I could do the same by putting the email address of the respective admin as request param value, but i don't want to the email address to appear in the url.
View Replies
View Related
Feb 11, 2014
if I declare
class Example
{
int x=10;
......
}
It is not showing any error but when I declare
class Example
{
int x;
x=10;
............
}
it showing compile time error ....
View Replies
View Related
Feb 18, 2014
int[][] array1 = {{1, 2, 3}, {}, {1, 2,3, 4, 5}};
it initializes 3 one dimentional array:
1 - {1, 2, 3}
2 - {}
3 - {1, 2,3, 4, 5}
but it only declares two dimensional arrays.
View Replies
View Related
May 11, 2014
consider:
class A {
final Object b;
public A(C c) {
try {
b = c.someMethodThatMayThrowSomeException();
} catch (SomeException e) {
b = null; // This line results in compiler error: "variable b might already have been assigned"
}
} // take away b=null line and you get "variable b might not have been initialized" on this line
}
Why? How could 'b' be assigned if the exception was thrown?
Btw, the workaround is to wrap the method call:
private final Object initB() {
try {
return c.someMethodThatMayThrowSomeException();
} catch (SomeException e) {
return null;
}
}
and use b = initB(); in the constructor. But that seems like it should be unnecessary.
View Replies
View Related
Nov 21, 2014
public class HashMapTest {
private static HashMap mp;
public static void main(String[] args) {
// TODO Auto-generated method stub
mp=new HashMap<String, String>();
}
}
This is My Code if I create Object in two place
1)Outside main() method but within class.
2)Inside main() method like above
Will these two approach makes any difference ?
I am asking a general senerio for creating any Type of Objects Primitives or References?
View Replies
View Related
Jan 29, 2015
I know that I can declare and initialize an member variable inside a class in a single statement but I can't do them on separate sentence. Why?
For example, I am allowed to do the following,
class A{
int a = 5;
// rest of the class
}
But I am not allowed to do this,
class A{
int a;
a = 5; // it doesn't compile even when the variable 'a' is static
// rest of the class
}
Why java don't allow me to do that?
View Replies
View Related
Jan 14, 2015
/*
* To change this license header, choose License Headers in Project Properties.
* To change this template file, choose Tools | Templates
* and open the template in the editor.
*/
package vecchiogiovane;
import java.io.*;
public class Vecchiogiovane {
/**
* @param args the command line arguments
*/
public static void main(String[] args) throws Exception{
[Code] .....
run:
run:
ins first name:
aldo
ins first age:
35
ins second name:
[Code] ....
View Replies
View Related
Apr 21, 2015
/*
* To change this license header, choose License Headers in Project Properties.
* To change this template file, choose Tools | Templates
* and open the template in the editor.
*/
package BaiVeNha;
import java.util.ArrayList;
import java.util.List;
import javax.swing.table.DefaultTableModel;
[Code] ....
View Replies
View Related
May 21, 2014
I've been trying to finish this blackjack program I have been making for my programming class, however, there are a few bugs I can't seem to iron out. It's a pretty short program, it's just that I'm an idiot and can't figure basic stuff like this out. Specifically, when I try and run it, I get this error:
Error occurred during initialization of VM
java.lang.OutOfMemoryError: unable to create new native thread
Java Code:
import static java.lang.System.*;
import java.applet.Applet;
import java.util.Scanner;
import java.io.*;
import java.util.Random;
import java.util.Date;
[Code] .....
So, obviously I'm doing something horribly wrong.
View Replies
View Related
Dec 13, 2014
how does recursion works, I don't understand why it prints al numbers going up again?This is the code
void print2(int n){
if (n<0){
out.printf(" %d",-1);
return;
}
out.printf(" %d", n);
print2(n-1)
out.printf(" %d", n);
}
this should be the output if n is 6: 6 5 4 3 2 1 0 -1 0 1 2 3 4 5 6.
View Replies
View Related
Mar 25, 2015
How to add the sum of an array with a recursion, but I don't understand how to use recursion. I just understand that it calls back the method. I am nearly done with the code.
import java.util.Scanner;
class Question1{
public static void main(String[]args){
Scanner s = new Scanner(System.in);
int size, sum;
System.out.println("Please input how many numbers will be used");
size=s.nextInt();
[Code] .....
View Replies
View Related
Aug 6, 2014
public void myFunc(MyNode n, ArrayList<MyNode> path) {
boolean hasChildren = false;
path.add(n);
int index = path.indexOf(n);
ArrayList<MyNode> statefulPath = new ArrayList<MyNode>();
[Code] ....
I have similar code that I stepped through in a debugger. After running the code I found that it built the desired tree, in this case a root node H with left child L and right child P. I want list of lists to contain all paths from root to leaf. I expected [H, L] and [H, P]. I discovered that statefulPath is not stateful; after a recursive stack frame pops, statefulPath still contains n! But that stack frame just popped! I expected to see statefulPath be [H] in the debugger and it was [H, L]! So I later have a list [H,L,P] which I don't want. How do I make the statefulPath list I want for my algorithm?
View Replies
View Related
Mar 22, 2015
I have a question related to the code below, that I do not understand. The aim is to count all files and subdirectories in an ArrayList full of files and subdirectories. So I have to count every file and every subdirectory.
The code concerning counting files is clear to me - every time d is of the type file I have to increment n by one. However I thought that I have to do the same thing in case d is a directory, so I would have written the same code for directories.
So what does "n += ((Directory) d).countAllFiles();" mean? In my understanding the method countAllFiles() is applied again on the object Directory ( as Directory is the class that contains this method), but how is n incremented by this? I thought n should be incremented by one as we did with files.
public int countAllFiles() {
int n = 0;
for(SystemFile d : content) {
if(d instanceof File) {
n++;
[Code] ....
View Replies
View Related
Jun 5, 2014
How the recursion works. I tried to figure out writing down low, mid, high at each recursive call. But I seem to be making a mistake somehow. I don't understand where the values are returned to in
if(leftmax>rightmax){
return leftmax;}
else
return rightmax;
Here's the code:
public class Maximum{
public static int max(int[] a,int low,int high){
int mid,leftmax,rightmax;
if(low==high)
return a[low];
[Code] ....
firstly leftmax=max(a,0,4)
Then what is the next line executed?Is it rightmax=max(a,5,8).
After this is it leftmax=max(a,5,6)
rightmax=max(a,7,8)
I tried to understand what these recursion calls by writing them down.But I somehow make a mistake.
View Replies
View Related
Oct 20, 2014
I just started studying recursion and I wanted to know how to create a palindrome number going up from 1 to n then back to 1 like this: "12345...n...54321".
I've done one going downwards and then upwards like this: "n...4321234...n".
Here's my code:
Java Code: import java.util.*;
public class PalindromeTest
{
public static void downPalindrome(int n)
[Code].....
View Replies
View Related
Jul 16, 2014
The program I'm working on is supposed to read input from a file and using recursion, print the pattern of asterisks for each value until the value is either < 0 or > 25.For example, if the value was 4, the pattern would look like this
*
* *
* * *
* * * *
* * *
* *
*
The values are stored in a file entitled prog3.dat which looks like this
4
3
15
26
0
I've never used recursion before and haven't been able to find anything showing how it would work with this particular type of problem.Here is what I've been able to come up with so far, but I'm having problems still which I will show following the code.
import java.util.Scanner;
import java.io.*;
public class Program3 {
public static void main(String[] args) throws Exception {
int num = 0;
java.io.File file = new java.io.File("../instr/prog3.dat");
Scanner fin = new Scanner(file);
[code]...
It appears to be reading the file correctly, but is only printing the top half of the pattern. Also, like I said, I'm not very familiar with recursion, so am not sure if this is actually recursion?
View Replies
View Related
